Electric tool

ABSTRACT

An electrical tool ( 1 ) includes an electric motor ( 3 ), a fan wheel ( 4 ) that is connected in torque-proof manner to a drive shaft ( 8 ) of the electric motor ( 3 ) disposed within a housing ( 2 ) that includes at least one air inlet aperture ( 6 ) and at least one air outlet aperture ( 7 ). The at least one air outlet aperture ( 7 ) is arranged axially apart from the fan wheel ( 4 ) with regard to the axis of rotation ( 10 ) of the drive shaft ( 8 ). An air guide baffle ring ( 11 ) encloses the fan wheel ( 4 ) coaxially and has at least one air duct ( 12 ) which leads to at least one air outlet aperture ( 7 ) located axially at a distance from the fan wheel ( 4 ) for cooling the electric tool ( 1 ).

REFERENCE TO RELATED APPLICATION

This application claims priority to German Patent Application No.102008059599.3-15 filed Nov. 28, 2008.

BACKGROUND

The present disclosure relates to an electrical tool, particularly ahand-operated electrical tool such as a drill or hammer drill.

An electrical tool of such kind is usually equipped with an electricmotor. A drive shaft of the electric motor may be connected in fixedmanner to a fan wheel in order to dissipate the heat generated in theelectric motor when the electrical tool is operated. A housing thataccommodates the electric motor and the fan wheel is furnished with atleast one air inlet aperture and at least one air outlet aperture. Whenthe electrical tool is being operated, the fan wheel is then able togenerate a flow of cooling air that passes from the respective air inletaperture and through the housing to the respective air outlet aperture.Besides exposing the electric motor to a flow of cooling air, thisarrangement enables cool air to pass over other heat-sensitivecomponents of the electrical tool, such as a gearbox, which acceleratesor slows the rotating speed of the drive shaft to match the speed forexample of a working spindle of the electrical tool.

SUMMARY

The present invention addresses the problem of suggesting an improveddesign for an electrical tool of the type described in the introduction,and that is characterized in particular in that it embodies an improvedcooling arrangement.

The disclosed electric tool includes an air guide baffle ring in thehousing to guide cooling air from the fan wheel to at least one airoutlet aperture. The air guide baffle ring is located separately fromthe fan wheel in the direction of the axis of rotation of the driveshaft. The at least one air duct of the air guide baffle ring enablesthe cooling air to be transported against a relatively weak flowresistance.

The at least one air duct may advantageously be conformed, andparticularly optimized, according to aerodynamic principles. The volumeflow of the exhaust air may be increased by reducing the flow resistanceto the exhaust air that is being conveyed by the fan wheel to the atleast one air outlet aperture. However, this is accompanied by theincreased volume flow of the intake air that is drawn in towards the fanwheel from the at least one air inlet aperture. Thus, the flow ofcooling air transported may be increased overall, with a resultingimprovement in cooling performance.

The air guide baffle ring also makes it possible to position air outletapertures at an axial distance from the fan wheel, because with weakflow resistance the at least one air duct is able to conduct the airflow from the fan wheel as far as the at least one air outlet aperture.Accordingly, new possibilities and capabilities become available for thedesign of both the housing and the electrical tool, since it is nolonger necessary to arrange the air outlet aperture one the same levelaxially as the fan wheel in order to be able to achieve a low flowresistance while maintaining adequate volume flow. Using the air guidebaffle ring enables the design of the electrical tool to be simplified.In particular, its construction may be more compact, because it is thenpossible to position the air outlet aperture and the fan wheel withaxial separation.

According to an embodiment, multiple air outlet apertures may beprovided in the housing, and in particular may be offset axiallyrelative to each other in the housing. The air guide baffle ring may nowinclude multiple air ducts, which lead to different air outletapertures, and in particular also to the air outlet apertures that areoffset axially. This modification also results in improved cooling,because multiple air outlet apertures in different locations may bereached via the air ducts, while the flow resistance may still be keptlow. Since the air ducts of the air guide baffle ring make it possibleto reach several air outlet apertures in various locations, furtheroptions are created for positioning air outlet apertures of such kind onthe housing. This increases freedom in the design of the electricaltool. In turn, it becomes easier to ensure an adequate flow of coolingair in the electrical tool. The total usable venting diameter may beincreased because appropriately arranged air ducts enable more airoutlet apertures of different kinds. This configuration may alsocontribute to reducing the flow resistance on the exhaust side. Thedirected air flow may also be used to cool parts of a gearbox in theelectrical tool. Air flow may be directed axially to such an extent thata part of the air flow is directed through the entire gearbox and doesnot escape from the device or housing until it reaches a front end areaof the electrical tool, e.g. close to a tool or drill chuck.

To achieve the aerodynamic optimization associated with reduced flowresistance, the respective air duct may have a tangential inlet areafacing the fan wheel and a radial outlet area assigned to the respectiveair outlet aperture.

Another embodiment includes an outside contour of the air guide bafflering that fits an inner contour of the housing in the area of the airguide baffle ring or of the fan. This enables the air guide baffle ringto match the shape of the housing in which it is installed. This in turnmakes it easier to install and position the air guide baffle ringimmovably inside the housing.

In order to improve the flow rate of the fan wheel on the exhaust side,which necessarily increases the cooling air volume flow and thus alsocooling capacity, other measures may be implemented instead of or inaddition to those cited, and in any combination. For example, the airguide baffle ring may coaxially enclose a fan wheel space in which thefan wheel is located. The respective air duct or ducts communicate withthis fan wheel space on the inlet side. The geometry of the fan wheelspace may be adapted to the radial outer contour of the fan wheel. Forexample, the fan wheel space includes a plurality of cylinder wallsections that form a relatively small radial gap between themselves andthe fan wheel. In this way, most if not all of the cooling air istransported away through the air ducts arranged circumferentiallybetween the cylinder wall sections, while only a small fraction of theair is directed through the annular gap in the radial direction. The airguide baffle ring may also have an annular base enclosing a centralinlet that communicates with the fan wheel space and at least partiallyoverlaps the fan wheel radially. Because of this annular base, supplyair that flows into the fan wheel space and fan wheel via the centralinlet is not able to return to the supply air side when it has beenforced outside into the area of the base through the fan wheel. The basethus blocks or prevents the air from flowing back, thus improving theflow rate of the fan wheel. A cap may also be provided to limit the fanwheel space axially on a side facing away from the base. This cap,through which in particular the drive shaft may pass, may also serve toblock or prevent false air flows escaping axially from the fan wheel andfan wheel space, thereby improving the radial flow rate of the fan wheelas well as the displacement of cooling air through the at least one airduct. This too ultimately increases the volume of the cooling air flow.

Of course, all of the features that have been described, as well asthose that will be explained below, may be implemented not only in thecombinations described for each, but also in other combinations or alonewithout thereby departing from the parameters of the invention.

Example embodiments of the invention are represented in the drawings andwill be explained in greater detail in the following description, inwhich identical or similar or functionally equivalent parts aredesignated with the same reference number. These and other featuresdisclosed herein can best be understood from the following specificationand drawings, the following of which is a brief description.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a side view of an electrical tool.

FIG. 2 is a lengthwise section of the electrical tool.

FIG. 3 is a cross section of the electrical tool along section lines IIIin FIG. 2.

FIG. 4 is a front view of an air guide baffle ring.

FIG. 5 is a lengthwise section of the air guide baffle ring alongsection lines V in FIG. 4.

FIG. 6 is a lengthwise section of the air guide baffle ring alongsection lines VI in FIG. 4.

FIG. 7 is a side view of the air guide baffle ring corresponding to aviewing direction VII in FIG. 4.

FIG. 8 is a rear view of the air guide baffle ring.

FIG. 9 is a perspective view of the air guide baffle ring.

DETAILED DESCRIPTION

As shown in FIGS. 1 to 3, an electrical tool 1 includes a housing 2, inwhich an electric motor 3 and a fan wheel 4 are disposed. The tool ispreferably a manually operated electrical tool, for which purpose itshousing 2 is equipped with a handle 5. In the example, electrical tool 1has the form of a hammer drill. It is also possible that the electricaltool may be a drill or saw, a grinder, a milling machine or similar.

Housing 2 is furnished with at least one air inlet aperture 6, throughwhich the air surrounding the electrical tool is able to enter theinterior of housing 2. In the example, three slot-like air inletapertures 6 are shown on the side facing the viewer in FIG. 1. Ofcourse, similar air inlet apertures 6 may also be present on the sidefacing away from the viewer. The positions and/or number of air inletapertures 6 may also differ from those shown in the illustration.Housing 2 is also furnished with at least one air outlet aperture 7. Inthe example, several air outlet apertures 7 are shown, in this casethree slot-shaped air outlet apertures 7 a, 7 b, 7 c, which in FIG. 1are located on a side of housing 2 facing the viewer. In this case too,of course, corresponding air outlet apertures 7 a, 7 b and 7 c may alsobe present on the side facing away from the viewer. As before, theposition and/or number of air outlet apertures 7 may differ from thoseshown. In addition, a fourth air outlet aperture 7 d is provided, and inFIGS. 1 to 3 is located on an underside of housing 2. It should be notedthat air outlet apertures 7 and air inlet apertures 6 are disposed ondifferent sides of electric motor 3 and fan wheel 4. With respect to acooling air flow that is generated inside housing 2 by air inletapertures 6 and extends to air outlet apertures 7, air inlet apertures 6are located upstream of electric motor 3, while air outlet apertures 7are located downstream thereof. The air returns to the atmosphere fromhousing 2 through air outlet apertures 7.

Fan wheel 4 is connected in torque-proof manner to a drive shaft 8 ofelectric motor 3. When electrical tool 1 is operating, fan wheel 4 isthus forced to rotate together with drive shaft 8. This causes fan wheel4 to impel the air, that is to say fan wheel 4 sucks ambient air inthrough air inlet apertures 6 and expels it out of housing 2 through airoutlet apertures 7. As a result, the desired cooling air flow is createdinside housing 2 to cool electric motor 3 and in particular may also beused to cool other components of electric tool 1. For example, thecooling air flow may also be used to cool a gearbox, which is not shownin detail here, or a bearing for drive shaft 8, which bearing is alsonot shown. Electronic components of electric tool 1, which are also notshown in detail here, might also be cooled actively.

First air outlet aperture 7 a is positioned approximately level with fanwheel 4 with reference to an axial line 9 that is defined by an axis ofrotation 10 of drive shaft 8 extending parallel thereto. All other airoutlet apertures 7 are arranged with axial separation from fan wheel 4on axial line 9. Thus, second air outlet aperture 7 b is axially distantfrom first air outlet aperture 7 a, and accordingly is axially distantfrom fan wheel 4. Similarly, third air outlet aperture 7 c is distant onaxial line 9 from the first two air outlet apertures 7 a and 7 b, and isthus yet more axially distant from fan wheel 4. In the example shown,fourth air outlet aperture 7 d is positioned farthest from fan wheel 4.Of course, it is possible for more air outlet apertures 7 to be presentand/or for them to be positioned differently. In particular, another airoutlet aperture, not shown here, may also be provided on housing 2,close to a tool chuck 23 at the opposite end of the tool from handle 5,for example so that a part of the cooling air flow is able to passcompletely through the gearbox referred to previously.

An air guide baffle ring 11 is located in housing 2. Air guide bafflering 11 surrounds fan wheel 4 coaxially and includes at least one airduct 12. In the example, several air ducts 12 are conformed on air guidebaffle ring 11, specifically one first air duct 12 a for each first airoutlet aperture 7, at least a second and third air duct 12 b and 12 cfor the second and third air outlet apertures 7 b and 7 c, and a fourthair duct 12 d for the fourth air outlet aperture 7 d. Air ducts 12 thusdirect the air from fan wheel 4 to air outlet apertures 7. In theexample, second air duct 12 b and third air duct 12 c converge or joinon both sides of tool 1 to lead to second and third air outlet aperture7 b, c as common air duct 12 b, c on the respective side of the tool. Atleast one of the air ducts 12, in this case the second, third and fourthair ducts 12 b, c, d, direct the air from fan wheel 4 to air outletapertures 7 that are axially distant from fan wheel 4, that is to say tothe second, third and fourth air outlet apertures 7 b, c, d. In theexample, at least one air duct 12, specifically the first two air ducts12 a, are constructed so as to lead to at least one air outlet aperture7, specifically to the first two air outlet apertures 7 a, which is/arelocated on axial line 9 close to fan wheel 4.

In the example shown, air guide baffle ring 11 also includes several airducts 12 leading to air outlet apertures 7 that are axially offsetrelative to each other. As was explained, at least three or four airducts 12 are allocated to the four air outlet apertures 7 a, b, c, daxially offset relative to each other and lead to these axially offsetair outlet apertures 7.

As shown in FIGS. 3 and 4, each air duct 12 has a tangential inlet area,not shown in detail, located radially towards the centre on a sidefacing towards fan wheel 4, and a radially aligned outlet area, notshown in detail, located radially towards the periphery on a side facingthe respective air outlet aperture 7.

As shown in FIG. 2 and also in FIGS. 4 to 9, air guide baffle ring 11shown here has a contour, not shown in detail here, that is conformed tomatch the inner contour of housing 2 in the area of fan wheel 4 and inthe area of air guide baffle ring 11. In this way, air guide baffle ring11 is able to be integrated in housing 2 with very little spacerequirement.

As shown in FIGS. 2 to 9, air guide baffle ring 11 coaxially encloses afan wheel space 13. Fan wheel 4 is located in this fan wheel space 13.Air ducts 12 also communicate with this fan wheel space 13 on the inletside. Air guide baffle ring 11 has multiple wall sections 14 thatdelimit fan wheel space 13 radially, and each of which delimits acircumferential segment of fan wheel space 13. Wall sections 14 may beconstructed as cylinder segments or may include at least one sectionhaving an interior in the shape of a cylinder segment. As shown in FIG.3, a relatively narrow radial gap 15 may be formed between wall sections14 and fan wheel 4, which prevents air from flowing radially outwards.The inlet areas of the various air ducts 12 are located between adjacentwall sections 14.

Air guide baffle ring 11 also has an annular base 16 that is arrangedcoaxially with axis of rotation 10 and encloses a central inlet 17 inair guide baffle ring 11. In addition, base 16 at least partly overlapsfan wheel 4 in the radial direction, as may be seen in FIG. 2. Centralinlet 17 communicates with fan wheel space 13. It faces towards theaxial intake side of fan wheel 4, whereas wall sections 14 face towardsthe radial pressure side of fan wheel 4. Air is drawn from housing 2through inlet 17, which also causes air to be drawn from the outside,through air inlet apertures 6 via the internal cooling air path. Base 16blocks or prevents the air from flowing back from the pressure side offan wheel 4 to its inlet side. As is shown in the example of FIG. 2, acap 18 is also provided to serve as the axial limit to fan wheel space13 on the side facing away from base 16. This cap 18 is advantageously apart that is manufactured separately from air guide baffle ring 11. Ithas a central aperture, not further shown here, through which driveshaft 8 passes. Cap 18 ensures that the air propelled by fan wheel 4flows from the pressure side through air ducts 12 and does not firstpass axially into housing 2. In this way, cap 18 assists with guidingthe air deliberately through air ducts 12, and also serves to reducedownstream side air resistance. Cap 18 rests axially flush with bearingsurfaces 19 that are provided on the frontal face of air guide bafflering 11. These bearing surfaces 19 are conformed on free frontal faceends of wall sections 14. Wall sections 14 serve as the radially inwardlimit for fan wheel space 13. They may also be extended into air ducts12 to form an inner and/or outer lateral limit for at least one of theair ducts 12.

As shown in FIG. 2 and also in FIGS. 4 to 9, air guide baffle ring 11 isalso equipped with an annular collar 20 that protrudes axially on a sidefacing away from fan wheel 4 and partially overlaps electric motor 3axially as shown in FIG. 2. This serves to channel and direct thecooling air path towards central inlet 17. In the example, axis ofrotation 10 of electric motor 3 in electrical tool 1 is aligned parallelto an axis of rotation 21 of a tool spindle 22 of electrical tool 1. Inall cases, the construction may also be angularly offset. The axialseparation between the air outlet apertures 7 at a distance from fanwheel 4 may be for example equal to and up to four times greater or atleast four times greater than an axial height of fan wheel 4.

The foregoing description is only exemplary of the principles of theinvention. Many modifications and variations are possible in light ofthe above teachings. It is, therefore, to be understood that within thescope of the appended claims, the invention may be practiced otherwisethan using the example embodiments which have been specificallydescribed. For that reason the following claims should be studied todetermine the true scope and content of this invention.

1. An electrical tool comprising: an electric motor (3); a fan wheel (4)that is connected in torque-proof manner to a drive shaft (8) of theelectric motor (3); a housing (2) that accommodates the electric motor(3) and the fan wheel (4), the housing having at least one air inletaperture (6) and at least one air outlet aperture (7), wherein at leastone such air outlet aperture (7) is arranged axially apart from fanwheel (4) with regard to the axis of rotation (10) of the drive shaft(8); and an air guide baffle ring (11) arranged in the housing (2)encloses the fan wheel (4) coaxially and has at least one air duct (12)which leads to at least one air outlet aperture (7) located axially adistance from the fan wheel (4).
 2. The electrical tool as recited inclaim 1, including multiple air outlet apertures (7), and wherein theair guide baffle ring (11) is furnished with multiple air ducts (12)which lead to different air outlet apertures (7).
 3. The electrical toolas recited in claim 1, including at least one additional air outletaperture (7 a) that is aligned axially in the area of the fan wheel (4),wherein the air guide baffle ring (11) is also provided with at leastone air duct (12 a) that leads to this at least one extra air outletaperture (7 a).
 4. The electrical tool as recited in claim 1, includingmultiple air outlet apertures (7) that are axially offset with respectto each other, wherein the air guide baffle ring (11) has multiple airducts (12) that lead to the axially air outlet apertures (7) that areaxially offset with respect to each other.
 5. The electrical tool asrecited in claim 1, wherein the respective air duct (12) has atangential inlet area and a radial outlet area.
 6. The electrical toolas recited in claim 1, wherein an outer contour of the air guide bafflering (11) is designed to complement an inner contour of the housing (2)in the area of the air guide baffle ring (11).
 7. The electric tool asrecited in claim 1, wherein the air guide baffle ring (11) coaxiallyencloses a fan wheel space (13) in which the fan wheel (4) is locatedand with which the respective air duct (12) communicates on the inletside.
 8. The electric tool as recited in claim 7, wherein the air guidebaffle ring (11) has an annular base (16) enclosing a central inlet (17)that communicates with the fan wheel space (13) and at least partiallyoverlaps the fan wheel (4) radially.
 9. The electric tool as recited inclaim 7, including a cap (18) that delimits the fan wheel space (13)axially.
 10. The electrical tool as recited in claim 9, wherein the cap(18) is axially flush with bearing surfaces (19) that are conformed onfrontal face ends of the fan wheel space (13) and/or wall sections (14)that laterally delimit the at least one air duct (12).
 11. Theelectrical tool as recited in claim 1, wherein the air guide baffle ring(11) has an axially protruding annular collar (20) on a side facing awayfrom the fan wheel (4), which collar at least partially overlaps theelectric motor (3) axially.
 12. The electrical tool as recited in claim1, wherein the electrical tool (1) is a drill or hammer drill.